#include<stdio.h>
#include<math.h>
int main()
{
    int i,count;
    printf("There are invetable primes with 4 digits:\n");
    for(count=0,i=1001;i<9999;i+=2)
    if(num(i))
    printf(count%9?"%3d:%d":"%3d:%d\n",++count,i);
}
num(int number)
{
    int j,i;
    if(!ok(number))return(0);
    for(i=number,j=0;i>0;i/=10)
    j=j*10+i%10;
    if(number<j)
    if(!ok(j))return(0);
    else return(1);
    else return(0);
}
ok (int number)
{
    int i,j;
    if(number%2==0)return(0);
    j=sqrt((double)number)+1;
    for(i=3;i<=j;i+=2)
    if(number%i==0)return(0);
    return(1);
}


//吴昌源